Shear wall holdowns and wall anchor connectors

ABSTRACT

A connector for securing a first building structural member to a second building structural member is provided. The connector includes a seat member with an opening for receiving an anchor bolt that secures the connector to the second building structural member. The connector also includes first and second side members that connect to the seat member and a back member that extends between the first and second side members, wherein the back member includes a plurality of shear openings for receiving shear fasteners that secure the connector to the first building structural member and resist shear forces only and at least one tension opening for receiving a tension fastener that secures the connector to the first building structural member and resists tension forces only.

FIELD OF THE INVENTION

[0001] The present invention relates generally a connector for abuilding structure and more particularly to a connector forstrengthening a connection between structural members of a building toprevent either major damage or failure of the structural members duringcataclysmic events such as earthquakes, high winds, hurricanes andtornadoes.

BACKGROUND

[0002] Earthquakes, high winds, hurricanes and tornadoes can imposecataclysmic forces on buildings that cause major and expensive damage aswell as structural failure. To counteract these forces, it has becomecommon practice to add connectors between the structural members of abuilding in areas where such cataclysmic forces can occur. For example,a connector can be added to strengthen a connection between a framedwall and a building foundation to increase resistance to shifting of theframed wall relative to the building foundation. Similarly a connectoris required to form a connection between a concrete or masonry wall andthe roof structure.

[0003] Current connectors are inadequate for the cataclysmic forces thatsome building structures require and/or have inefficient designs thatrequire too many fasteners to mount the connector to the buildingstructure. Accordingly, a need exists for an improved connector forstrengthening the connections between structural members of a building.

SUMMARY

[0004] In one embodiment, the present invention includes a connector forsecuring a first building structural member to a second buildingstructural member. The connector includes a seat member with an openingfor receiving an anchor bolt that secures the connector to the secondbuilding structural member. The connector also includes first and secondside members that connect to the seat member and a back member thatextends between the first and second side members, wherein the backmember includes a plurality of shear openings for receiving shearfasteners that secure the connector to the first building structuralmember and resist shear forces only and at least one tension opening forreceiving a tension fastener that secures the connector to the firstbuilding structural member and resists tension forces only.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] These and other features and advantages of the present inventionwill be better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings wherein:

[0006]FIG. 1A is a perspective view of an exemplary embodiment of aconnector according to the present invention;

[0007]FIG. 1B is a cross sectional view of the connector of FIG. 1A,wherein the connector is secured to a first building structural memberand to a second building structural member;

[0008]FIG. 2A is a front view of an exemplary embodiment of a connectoraccording to the present invention;

[0009]FIG. 2B is a side view of the connector of FIG. 2A;

[0010]FIG. 3A is a front view of another exemplary embodiment of aconnector according to the present invention;

[0011]FIG. 3B is a side view of the connector of FIG. 3A;

[0012]FIG. 4A is a front view of another exemplary embodiment of aconnector according to the present invention;

[0013]FIG. 4B is a side view of the connector of FIG. 4A.

[0014]FIG. 5A is a front view of another exemplary embodiment of aconnector according to the present invention;

[0015]FIG. 5B is a side view of the connector of FIG. 5A;

[0016]FIG. 6 is a side view of an exemplary shear fastener for use witha connector according to the present invention; and

[0017]FIG. 7 is a side view of an exemplary tension fastener for usewith a connector according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0018] As shown in FIGS. 1A-1B, an exemplary embodiment of the presentinvention is directed to a connector 10 for strengthening a connectionbetween a first building structural member 22 and a second buildingstructural member 28 through a wood sill plate or ledger member 27. Forexample, the first building structural member 22 may be a wooden stud orroof or floor frame member and the second building structural member 28may be a building foundation, such as a concrete foundation, or aconcrete or masonry wall.

[0019] The connector 10 includes a seat member 12, a first side member16 connected to the seat member 12, a second side member 18 connected tothe seat member 12, and a back member 20 extending between the first andsecond side members 16 and 18. The seat member 12 includes an opening 24for receiving an anchor member 26 that secures the connector 10 to thesecond building structural member 28. The back member 20 includes aplurality of openings (as will be discussed in detail below) forreceiving fasteners that secure the connector 10 to the first buildingstructural member 22.

[0020] For example, in one embodiment the back member 20 includes aplurality of shear openings 30, such as substantially circular openings,and at least one tension opening 32, such as a vertically slottedopening. The shear openings 30 are for receiving fasteners 34(hereinafter shear fasteners 34) that secure the connector 10 to thefirst building structural member 22 and resist shear forces S₁ only. Theat least one tension opening 32 is for receiving a fastener 36(hereinafter tension fastener 36) that secures the connector 10 to thefirst building structural member 22 and resists tension forces T₂ only.

[0021] Connectors of the prior art have back members with openings forreceiving fasteners that are responsible for resisting both shear andtension forces. By contrast, the connector 10 of the present inventionincludes the back member 20 having shear openings 30 for receiving shearfasteners 34 that resist shear forces only and at least one tensionopening 32 for receiving tension fasteners 36 that resist tension forcesonly. By dividing the forces acting on the connector 10 into tensionforces and shear forces, the connector 10 is able to resist a largeramount of force using less fasteners than is possible using connectorsof the prior art, where the fasteners must simultaneously resist bothshear and tension forces.

[0022]FIG. 1B, shows the connector 10 attached to a first buildingstructural member 22 and a second building structural member 28, as wellas some of the forces acting on the connector 10, the first buildingstructural member 22, and the second building structural member 28. Forexample, T₁ is a tension force that external forces exert on the firstbuilding structural member 22. This tension force T₁ is also equal andopposite to the tension force on the anchor member 26. E₁ is aneccentric force between the two opposing tension forces T₁. Theeccentric force E₁ is resisted by the first building structural member22 in combined tension and bending. S₁ is a resultant of total sheardeveloped by the shear fasteners 34 that are in bearing against thefirst building structural member 22. E₂ is an eccentric force betweenthe combined bearing force S₁ of the shear fasteners 34 and the tensionforce T₁ on the anchor member 26. The eccentric force E₂ creates amoment that is resisted by the connector 10. This moment is alsoresisted by the tension fastener 36 with force T₂ and an equal force B₂that bears against the first building structural member 22 at the baseof the connector 10.

[0023] In one embodiment, as shown in FIGS. 2A and 2B, the shearopenings 30 are arranged in at least two rows 38 that each have at leasttwo shear openings 30. Each shear opening 30 may have the same or asimilar shape, such that each shear opening 30 accommodates a similarsized shear fastener 34. For example, each shear opening 30 may becircular and have substantially the same diameter.

[0024] Each row 38 of shear openings 30 is vertically spaced apart by adistance B from its vertically adjacent row or rows 38, with thelowermost row 38 being vertically spaced a distance C from a bottomsurface of the seat member 12. Each row 38 may also be laterallystaggered from its vertically adjacent row or rows 38. For example, inthe depicted embodiment, each row 38 is laterally staggered a distance Afrom its vertically adjacent row 38. In addition, the shear openings 30of each row 38 may be laterally spaced apart by a distance of 2A. Alsoin the depicted embodiment, the shear opening 30 that is laterallynearest to the first side member 16 is spaced a lateral distance E froman outer surface of the first side member 16 and the shear opening 30that is laterally nearest to the second side member 18 is spaced thelateral distance E from an outer surface of the second side member 18.

[0025] Preferably, the at least one tension opening 32 is disposed in anupper portion of the connector 10 and is formed as a vertical slot. Inthe depicted embodiment, the at least one tension opening 32 isdisplaced a vertical distance D from the uppermost row 38 of shearopenings 30. In embodiments where the connector 10 includes one tensionopening 32, it is preferred that the tension opening 32 is approximatelycentered with respect to a width W of the connector 10. In embodimentswhere the connector 10 includes more than one tension opening 32, it ispreferred that the tension openings 32 are symmetrically spaced withrespect to the vertical axis of the connector 10 (as shown in FIG. 5A).

[0026] The first side member 16, the second side member 18, the backmember 20 and the seat member 12 may form one integral part.Alternatively, one or more of the components may be welded to one ormore of the other components. For example, in one embodiment the firstside member 16, the second side member 18 and the back member 20 formone integral part that is welded to the seat member 12. Preferable, theconnector 10 is made of a structural steel, such as ASTM A-36. Thethickness and physical dimension of members 12, 16, 18 and 20 aredetermined by the strength required to resist the movement anddeflection caused by the eccentricity E₂ (as shown in FIG. 1B) betweenthe anchor member 26 and the adjacent face of the wood member 22.

[0027] In the depicted embodiment, the seat member 12 laterallyprotrudes from the side members 16 and 18. The seat member opening 24 islaterally displaced a distance F from a back surface of the back member20 along a length L of the connector 10 and is preferably approximatelycentered with respect to the width W of the connector 10.

[0028] For ease of installation, the connector 10 may include one ormore installation openings 40. The installation openings 40 are forreceiving installation fasteners for securing the connector in positionprior to installation of the shear fasteners 34 and tension fasteners36. Preferably, the installation openings 40 are centered about thevertical axis of the connector 10.

[0029] In exemplary embodiments, any or all of the distances A, B, C, Dmay have the following relationships with respect to the lag screw andthrough bolt diameter of the shear fastener 34 that is received by eachshear opening 30:

[0030] In keeping with the requirements for staggered fasteners in the2001 National Design Standards for Wood Construction published by theAmerican Forest and Paper Association, the distance A is equal to atleast one and one half times, or alternatively approximately one and onehalf times, the diameter of the shear fastener 34 that is received byeach shear opening 30.

[0031] The distance B is equal to at least six times, or alternativelyapproximately six times, the diameter of the shear fastener 34 that isreceived by each shear opening 30, wherein six times the diameter of theshear fastener 34 is also equal to four times the distance A.

[0032] The distance C is equal to at least seven times, or alternativelyapproximately seven times, the diameter of the shear fastener 34 that isreceived by each shear opening 30.

[0033] The distance D is equal to at least six times, or alternativelyapproximately six times, the diameter of the shear fastener 34 that isreceived by each shear opening 32.

[0034] The dimension F is selected to minimize the eccentricity E₁ andE₂ (as shown in FIG. 1B) between the back member 20 of the connector 10and the anchor member 26 in the concrete foundation 28 for wood framewall holdowns (HD).

[0035] The dimension F can be chosen to create a spacing large enough toaccommodate 12 adjacent anchor member 26 diameters for paired anchorconnectors (AC) attaching minimum 4-inch width wood roof members toconcrete or masonry walls. A spacing of 12 anchor bolt 26 diametersminimum is required to develop the full anchor capacity in concretewalls.

[0036] Any or all of the distances A, B, C, D may be less than theminimums described above, however, this creates a risk of splitting thewood when the first building structural member 22 is wooden.

[0037] The following table shows exemplary embodiments of the connector10 corresponding to the embodiments depicted in FIGS. 2A-5B. Forclarity, each embodiment is referred to as FIG. 2, FIG. 3, . . . etc.rather than the embodiment depicted in FIGS. 2A-2B, the embodimentdepicted FIGS. 3A-3B, . . . etc. Although the table depicts the use of{fraction (1/4)} inch diameter lag screw shear fasteners 34 and{fraction (5/16)} inch diameter lag screw tension fasteners 36, nothingprecludes the use of through bolts to develop required loads that exceedthe particular limit of 24 shear fasteners 34. In the table, alldimensions are in inches except the design load capacity of theconnector 10 which is given in pounds. No. of rows 34 1 2 2  4 No. ofshear fasteners 4 6 6 10 34 Dia. of shear openings 9/32 9/32 9/32 9/3230 Dimensions of shear ¼ Dia. × 2 ¼ Dia. × 2 ¼ Dia. × 1¾ ¼ Dia. × 1¾fasteners 34 Long Long Long Long No. of tension 1 1 1 2 openings 32Dimensions of tension {fraction (7/16)} × {fraction (11/16)} {fraction(7/16)} × {fraction (11/16)} {fraction (7/16)} × {fraction (11/16)}{fraction (7/16)} × {fraction (11/16)} openings 32 Dimensions of tension{fraction (5/16)} Dia. × 1¾ {fraction (5/16)} Dia. × 1¾ {fraction(5/16)} Dia. × 1¾ {fraction (5/16)} Dia. × 1¾ fasteners 36 Long LongLong Long No. of installation 2 2 2  2 openings 40 Dia. of installation5/32 5/32 5/32 5/32 openings 40 Dimension of #6 Dia. × 1 #6 Dia. × 1¼ #6Dia. × 1¼ #6 Dia. × 1½ installation fasteners Long Long Long Long Dia.of seat member ⅝ ¾ ⅝ ⅞ opening 24 Dimensions of anchor ½ Dia. ⅝ Dia. ½Dia. ¾ Dia. screw 26 A ⅜ ⅜ ⅜ ⅜ B 1½ 1½ 1½  1½ C 1⅞ 1⅞ 1⅞  1⅞ D 1¾ 1¾ 1¾ 1¾ E ⅝ ⅝ ⅝ ¾ F 1⅜ 1¾ 1⅞  2¼ H 6 7½ 7½ 10½ W 2⅜ 2⅜ 2⅜  2⅝ L 2 2⅛ 2½  3½

[0038]FIG. 6 shows an exemplary shear fastener 34 that may be used withthe connector 10 of the present invention. The shear fastener 34 may bea lag screw or a standard through bolt, among other suitable fasteners.In the depicted embodiment, the shear fastener 34 is a specialized lagscrew having a length L₁ that is divided into a tip section 44, athreaded shank section 46 and an unthreaded shank section 48.

[0039] The tip section 44 may include an angled cutting tip 45. In oneembodiment, the cutting tip 45 has an angle of approximately 90 degreeswith respect to a longitudinal axis 54 of the fastener 34. The cuttingtip 45 facilitates inserting the shear fastener 34 into the firstbuilding structural member 22, such as a wooden stud or a wooden framemember. The 90 degree cutting tip 45 provides optimum cutting of woodgrain to allow the shear fastener 34 to be installed using, for example,an electric drill without the need for predrilling an opening into thefirst building structural member 22.

[0040] In one embodiment, the shear fastener 34 has a shank diameter D₁of {fraction (1/4)} inches and a length L₁ of at least 1¾ inches oralternatively approximately 1¾ inches. The 1¾ inch length is the optimumdimension when the first building structural member 22 is either a 2inch thick wood member or a 4 inch thick wood member, since longerlengths could interfere with fasteners installed on an opposite side ofthe first building structural member 22, and the 1¾ inch length developsthe same shear value or resistance to shear as longer lag screws thatare 11 gage or thicker. Fasteners that are shorter than the 1¾ inchlength develop a less than optimum shear value.

[0041] Preferably, the length L₁ includes a tip section length ofapproximately {fraction (1/4)} inch, a threaded shank section length ofapproximately 1 inch and an unthreaded shank section length ofapproximately ½ inch. In this embodiment, a threaded section 50 of theshear fastener 34 is at least or approximately 1¼ inches, which is,respectively, at least or approximately four times the diameter of theshank diameter D₁. The threaded section 50 may include rolled threadshaving, for example, 10 threads per inch. The ½ inch length of theunthreaded shank section 48 provides a full diameter bearing of thefastener against the grain of the wood when the first buildingstructural member 22 is a wooden member.

[0042] In the depicted embodiment, the shear fastener 34 includes a head55 having an integral washer 52 with locking nodules 53 extendingtherefrom, such that when the shear fastener 34 is inserted through oneof the plurality of shear openings 30 in the back member 20 of theconnector 10 and into the first building structural member 22, thelocking nodules 53 bear into and secure the shear fastener 34 againstthe back member 20 of the connector 10. The head 55 with its integralwasher 52 and locking nodules 53 is positioned adjacent to theunthreaded shank section 48 and in one embodiment, is a {fraction (3/8)}inch hexagonally shaped head. In one embodiment, the shear fasteners 34is composed of a steel material, such as cold head quality C1018 that isannealed, black oxide coated and waxed.

[0043]FIG. 7 shows an exemplary tension fastener 36 that may be usedwith the connector 10 of the present invention. The tension fasteners 36is similar to the shear fasteners 34 except that preferably, the tensionfastener 36 has a shank diameter D1 of {fraction (5/16)} inches androlled threads having, for example, 9 threads per inch. As with theshear fastener 34, preferably, the tension fastener 36 has a head 56that is a {fraction (3/8)} inch hexagonally shaped head so that thesocket size is the same for both fasteners, shear 34 and tension 36.Currently available {fraction (5/16)} inch diameter lag screws have a{fraction (7/16)} inch hexagonally shaped head rather than the preferred{fraction (3/8)} inch hexagonally shaped head for the tension fastener36 of the present invention.

[0044] The tension fastener 36 includes an integral washer 51 formedwith the head 56. A washer 57 may be loose from the head 56. When thetension fastener 36 is inserted through one of the at least one tensionopenings 32, such as a vertically slotted opening, in the back member 20of the connector 10 and into the first building structural member 22,the washer 57 helps to minimize friction between the tension fastener 36and the back member 20 of the connector 10.

[0045] The preceding description has been presented with reference topresently preferred embodiments of the invention. Persons skilled in theart and technology to which this invention pertains will appreciate thatalterations and changes in the described structures and methods ofoperation can be practiced without meaningfully departing from theprinciple, spirit and scope of this invention. Accordingly, theforegoing description should not be read as pertaining only to theprecise structures described and shown in the accompanying drawings, butrather should be read as consistent with and as support for thefollowing claims, which are to have their fullest and fairest scope.

What is claimed is:
 1. A connector for securing a first buildingstructural member to a second building structural member comprising: aseat member having an opening for receiving an anchor bolt that securesthe connector to the second building structural member; a first sidemember connected to the seat member; a second side member connect to theseat member; and a back member extending between the first and secondside members, wherein the back member includes a plurality of shearopenings for receiving shear fasteners that secure the connector to thefirst building structural member and resist shear forces only and atleast one tension opening for receiving a tension fastener that securesthe connector to the first building structural member and resiststension forces only.
 2. The connector of claim 1, wherein each shearopening is substantially circular and each tension opening is a verticalslot.
 3. The connector of claim 1, wherein the shear openings arearranged in at least two rows that each have at least two shearopenings.
 4. The connector of claim 3, wherein each row is laterallystaggered from a vertically adjacent row.
 5. The connector of claim 4,wherein each row is laterally staggered from a vertically adjacent rowby a distance from of at least 1½ times the diameter of the shearfasteners that are inserted into the plurality of shear openings.
 6. Theconnector of claim 3, wherein each shear opening of each row isvertically spaced apart by a distance of at least six times the diameterof the shear fasteners that are inserted into the plurality of shearopenings.
 7. The connector of claim 3, wherein a lowermost row of the atleast two rows is vertically spaced from a bottom surface of the seatmember by a distance of at least seven times the diameter of the shearfasteners that are inserted into the plurality of shear openings.
 8. Theconnector of claim 3, wherein each of the at least one tension openingsis vertically spaced apart from an uppermost row of the at least tworows by a distance of at least six times the diameter of the shearfasteners that are inserted into the plurality of shear openings.
 9. Theconnector of claim 1, wherein each shear fastener and each tensionfastener is a lag screw having a length that is divided into a tipsection, a threaded shank section that is adjacent to and integrallyformed with the tip section and an unthreaded shank section that isadjacent to and integrally formed with the shank section, wherein thetip section includes an angled cutting tip that is cut at an angle ofapproximately 90 degrees with respect to a longitudinal axis of eachfastener.
 10. The connector of claim 1, wherein each shear fastener andeach tension fastener has a length of approximately 1¾ inches, anunthreaded shank section length of approximately ½ inch, anapproximately {fraction (3/8)} inch hexagonally shaped head and whereinthe diameter of each shear fastener is approximately {fraction (1/4)}inch and the diameter of each tension fastener is approximately{fraction (5/16)} inch.
 11. The connector of claim 1, wherein each shearfastener comprises a head, wherein each head has an underside having aplurality of locking nodules disposed thereon.
 12. A connector forsecuring a first building structural member to a second buildingstructural member comprising: a seat member having an opening forreceiving an anchor bolt that secures the connector to the secondbuilding structural member; a first side member connected to the seatmember; a second side member connect to the seat member; and a backmember extending between the first and second side members, wherein theback member includes a plurality of substantially circular shearopenings for receiving shear fasteners that secure the connector to thefirst building structural member and resist shear forces only and atleast one vertically slotted tension opening for receiving a tensionfastener that secures the connector to the first building structuralmember and resists tension forces only, wherein the shear openings arearranged in at least two rows that each have at least two shear openingsand wherein each row is laterally staggered from a vertically adjacentrow.
 13. The connector of claim 12, wherein each row is laterallystaggered from a vertically adjacent row by a distance from ofapproximately 1½ times the diameter of the shear fasteners that areinserted into the plurality of shear openings.
 14. The connector ofclaim 12, wherein each shear opening of each row is vertically spacedapart by a distance of approximately six times the diameter of the shearfasteners that are inserted into the plurality of shear openings. 15.The connector of claim 12, wherein a lowermost row of the at least tworows is vertically spaced from a bottom surface of the seat member by adistance of approximately seven times the diameter of the shearfasteners that are inserted into the plurality of shear openings. 16.The connector of claim 12, wherein each of the at least one verticallyslotted tension openings is vertically spaced apart from an uppermostrow of the at least two rows by a distance of approximately six timesthe diameter of the shear fasteners that are inserted into the pluralityof shear openings.
 17. The connector of claim 12, wherein each shearfastener and each tension fastener is a lag screw having a length thatis divided into a tip section, a threaded shank section that is adjacentto and integrally formed with the tip section and an unthreaded shanksection that is adjacent to and integrally formed with the shanksection, wherein the tip section includes an angled cutting tip that iscut at an angle of approximately 90 degrees with respect to alongitudinal axis of each fastener.
 18. The connector of claim 17,wherein each shear fastener and each tension fastener has a length ofapproximately 1¾ inches, an unthreaded shank section length ofapproximately ½ inch, an approximately {fraction (3/8)} inch hexagonallyshaped head and wherein the diameter of each shear fastener isapproximately {fraction (1/4)} inch and the diameter of each tensionfastener is approximately {fraction (5/16)} inch.
 19. The connector ofclaim 17, wherein each shear fastener comprises a head, wherein eachhead has an underside having a plurality of locking nodules disposedthereon.
 20. A lag screw comprising: a predetermined diameter; a lengththat is divided into a tip section, a threaded shank section that isadjacent to and integrally formed with the tip section and an unthreadedshank section that is adjacent to and integrally formed with the shanksection, wherein the tip section includes an angled cutting tip that iscut at an angle of approximately 90 degrees with respect to alongitudinal axis of the screw; and a head on the unthreaded shanksection at an end of the screw that is opposite the tip section.
 21. Thelag screw of claim 20, wherein an underside of the head comprises aplurality of locking nodules.
 22. The lag screw of claim 21, wherein thelength is approximately 1¾ inches, the unthreaded shank section isapproximately ½ inch in length, the head is an approximately {fraction(3/8)} inch hexagonally shaped head and the diameter is approximately{fraction (1/4)} inch.
 23. The lag screw of claim 20, wherein the lengthis approximately 1¾ inches, the unthreaded shank section isapproximately ½ inch in length, the head is an approximately {fraction(3/8)} inch hexagonally shaped head and the diameter is approximately{fraction (5/16)} inch.